Tone amplifier for pianos



2, 1940- R. w. E. SPERRY 2, 06,650

TONE AMPLIFIER FOR PIANOS Filed Nov. 19, 1938 2 Sheets-Sheet 1 I 5 5 z I[Z I "j 15. [4 I f INVENTOR. 1691/ 1445. $7524):

A- 1 ORNEYi 2, 1940- R. w. E. SPERRY 2,206,650

TONE AMPLIFIER FOR PIANOS Filed Nov.- 19, 1938 2 Sheets-Sheet 2INVENTOR. 2674 PH 14 E. .SPf/FE).

Patented July 2, .1940

PATENT OFFICE v 2,208,650 TONE AMPLIFIER FOR PIANOS Ralph w. E. Sperry,De Kalb, 111., assignor to The Rudolph Wurlitzer Company, Cincinnati,

Ohio, a corporation Application November 19, 1938, Serial No. 241,297

7 Claims.

.This invention relates to a structure for amplifying the tone of apiano, and particularly for carrying the string vibrations toward themiddle portion of the sounding board, being particularly 5 applicable tothe smaller piano structures necessitating the bridge being located toonear to the fixed edge of the sounding board.

It has been found that in the smaller piands, and particularly such asare commonly known as the baby grand or the butterfly grand,

there is not sufficient room within the casing to permit locating thestring bridge sufiiciently distant from the fixed edge of the soundingboard to give the desired deep mellow tone. Thus, wherein the longerstrings, such as the higher treble and bass strings, extendsubstantially the full width of the piano casing, this problemparticularly arises and results in a deadening oi the sound because ofinsufficient freedom of vibration oi the sounding board wherethe bridgeoperates too closely to the casing.

To improve these conditions, and as particularly applied to the longerstrings, it has been found that the deeper more mellow tone may stringvibration not only directly through the bridge to the sounding board,but in addition through the bridge to a lever extending toward themiddle portion of the sounding board so as to transmit vibrationsthereto. This arrangement may take several forms of structure.

vThat herein more specifically disclosed pertains primarily to thehigher treble strings, a differenttype of lever arrangement beingrequired for the bass strings. However, the same invention as hereindisclosed applies equally to both. More specifically, a lever in theform of a metal or wooden strip is provided having one end firmlyanchored to the frame and extending 40 therefrom toward the, middleportion of the sounding board where its inner end bears thereon. Saidstrip extends across the bridge in contact therewith so that vibrationsset up by the strings through the bridge will be transmitted throimh thearm to the sounding board.

In another form, the lever arm has its inwardly extending free endmerely in fixed or adjustable contact with the middle portion of' thesounding board. It is sumcient for the purpose of this invention thatprovision be made to transmit the vibrations set up in the bridge by thestrings inwardly of the sounding board.v

The full-nature of the invention will be understood from theaccompanying drawings and the following description and claims:

Fig. 1 is a sectional view through the bridge and sounding board of apiano with one form r of lever construction mounted thereon. Fig. 2 is aplan view illustrating one type of bridge and the pomtion of the leverwith respect thereto be obtained by providing means to transmit the andthe treble strings. Fig. 3 is the same'as Fig. 1, showing a modifiedform of lever construction. Fig, 4 is the same as Figs. 1 and 3, showinga further modified form. Fig. 5 is the same as Fig. 1 showing stillanother modification. 'Fig. 6 is the same as Hg. 2 illustrating theinvention as applied to the usual bridge construction.

In the drawings there is shown a portion of a piano having a casing i8and metal plate i l to which is secured a pin block i 2 having thestring pins l3 thereon. Anchored to the pins i3 are the usual treblestrings M which extend over and bear upon the bridge E5. The bridge ismounted in the usual manner upon the sounding board It supported by theribs H, the peripheral edge of the sounding board being secured to theframework i8 in the usual manner. Adjacent the end of the bridge i 5near the higher treble strings, the bridge is notched on its undersideto provide an opening indicated at l9 through which a vibrationtransmitting lever arm 20 extends.

The lever arm 20 is arrangedto extend crosswise of the bridge from theframe I8 toward the middle portion of the sounding board. One '25 end'ofthe lever arm is rigidly secured and anchored .between the framestructure and the plate II or pin block. As shown in Fig. 1, the otherend of the arm is rigidly secured by a suitable screw 2| at or near themiddle portion thereof, but preferably spaced therefrom by a block 22.An adjusting screw 23, extending through the bridge l5 and having itsand bearing upon the lever arm 20, may be employed to adjust thetensionof the lever arm with respect to the bridge and sounding board. b

There may be one or more such lever arms employed at spaced intervalsalong the bridge, either in respect to the treble strings or the bassstrings, or both. As shown herein, it is sufficient, so far'as thetreble strings are concerned, that a single lever arm be locatedadjacent that end of the bridge on which the higher treble strings bear.

The result of this arrangement is that that group of strings bearingupon the portion of the bridge lying closest to the frame not onlypermits vibration directly through the bridge to the sounding board, butthrough the bridge to the lever arm 20 which in turn transmits thevibrations to the middle'portlon or the sounding board. Thus, thevibrations normally transmitted to the sounding board atthat portionalong which the bridge bears is amplified by the further transmission ofvibrations to the middle 0 portion of the board. In the modified formshown in Fig. 3, the lever arm I20 is provided with an adjustable screw-l2i which bears upon a metal plate I22 which initurn bears upon thesounding board. Thus, 60

In the modified form, as shown in Fig. 4, the

lever arm extends over instead of under the bridge. Thus, there is shownan arm 22!! having in its inner end an adjustable screw 22l extendingtherethrough and bearing upon a washer 222 which in turn bears upon thesounding board. In this structure, there is also an adjustable screw 223extending into the top of the bridge and adjustably spacing the leverarm thereabove. For anchoring the opposite end of the lever arm to theframe, a block 224 is provided to which it is secured, the block in turnbeing secured to the pin block or plate.

In the modified form, as shown in Fig. 5, the lever arm 320 is gluedsecurely-to the bridge under which it extends, as indicated at 323. Theinner end of the leverarm is likewise glued to the block 32L which is inturn glued to the upper surface of the sounding board.

In the illustrative plan view shown in Fig. 2, the bridge H5 isterminated short of the higher treble strings, being supplemented by arrexpansion bridge H6 which .extends across the sounding board inchord-like fashion so as not to be too closely located with respect tothe piano frame. In this construction, the lever arm, herein shown asthat of Fig. 1, extends under the chord-like extension H6 toward themiddle portion of the sounding board.

In the illustrative plan view shown in Fig. 6, the bridge 215 extends toall the treble strings. In this construction, the lever arm, likewiseshown as that of Fig. 1, extends under the bridge 2l5 near its end andtoward the middle portion of the sounding board upon which it bears.

The invention claimed is:

' 1. In a piano structure the combination with a supporting frame, asounding board secured thereto, and a string plate having a pin blockthereon to which the respective strings are secured, of a bridgesupported by the sounding board having a portion thereof approaching theframe over which the strings bear for transmitting vibration to thesounding board, and a lever arm extending substantially transversely toand in contact with said bridge, one end being secured to said frame andthe other end extending inwardly toward the middle portion of thesounding board and bearing thereon for transmitting vibrations from thebridge to the sounding board.

2. In a piano structure the combination with a supporting frame, asounding board secured thereto, and a string plate having a pin blockthereon to which the respective strings are secured, of a bridgesupported by the sounding board having a portion thereof approaching theframe over which the strings bear for transmitting vibration to thesounding board, a lever arm extending substantially transversely to and.in contact with said bridge, one end being secured to said frame and theother end extending inwardly toward the middle portion of thesoundingboard and bearing thereon for transmitting vibrations from the bridge tothe sounding board, and adjustable means associated with said lever armfor varying the bearing pressure thereof on the bridge andsoundingboard.

3. In a piano structure the combination with a supporting frame, asounding board secured thereto, and a string plate having a pin blockthereon to which the respective strings are secured, of a bridgesupported by the sounding board terminating short of the higher treblestrings, and a chord-like bridge extension having one end secured to thefirst-mentioned bridge and extending transversely of the higher treblestrings, said extension lying a substantial distance inwardly from thepin block and bearing the higher treble strings for transmitting theirvibra tions to the sounding board at a greater distance inwardly fromthe pin block than the first-mentioned bridge.

4. In a piano structure the combination with a supporting frame, asounding board' secured thereto, and a string plate having a pin blockthereon to which the respective strings are secured, of a bridgesupported by the sounding board terminating short of the higher treblestrings, a chord-like bridge extension having one end secured to thefirst-mentioned bridge and extending transversely of the higher treblestrings, said extension lying a substantial distance inwardly from thepin block and bearing the higher treble strings for transmitting theirvibrations to the sounding board at a greater distance inwardly from thepin block than the first-mentioned bridge,and a lever arm havingone endsecured to the frame and extending inwardly substantially transverselyof said bridge extenthereto, and'a series of piano strings connectedwith said frame and extending over said board,

of a vibration transmitting lever arm having one end secured to saidframe and extending inwardly therefrom toward the middle portion of thesounding board and bearing on said sounding board for transmitting thevibrations set up in said strings inwardly from the frame to thesounding board near the middle portion thereof.

6. In a piano structure, the combination with a supporting frame, asounding board secured thereto, and a string plate having a pin blockthereon to which the respective piano strings are secured, of a bridgesupported by the sounding board adjacent said frame over which thestrings bear for transmitting vibrations to said board, and auxiliarymeans bearing against said bridge and board extending inwardly from thebridge over the upper surface of the board toward the middle portionthereof for transmitting a portion of said vibrations directly from thebridge to the middle portion of the board.

'7. In a piano structure, the combination with a supporting frame, asounding board secured thereto, and a string plate having a pin blockthereon to which the respective strings are secured, of a bridgesupported by the sounding board over which the strings bear fortransmitting vibrations thereto', and a lever arm bearing against saidbridge and extending substantially transversely thereof over the uppersurface of the sounding board toward the middle portion thereof with theextended end of said arm-bearing upon said sounding board fortransmitting vibrations thereto. 1

RALPH W. E. SPERRY.

